Embodiments of the inventive concept relate generally to electronic memory technologies. More particularly, embodiments of the inventive concept relate to trim circuits for memory devices, and memory devices and memory test systems incorporating the trim circuits.
Semiconductor manufacturing processes have variations that can cause minor differences in manufactured semiconductor devices. These differences can cause the semiconductor devices to have operating characteristics that differ from those intended by a designer. As examples, minor variations in layer deposition or curing processes can cause certain layers of a semiconductor memory device to have higher or lower resistances than intended, which can cause the operating voltages of the device to be slightly different from intended operating voltages.
To address the effects of manufacturing variances and other sources of device variation, semiconductor memory devices commonly include elements for adjusting certain operating characteristics following manufacture. As an example, many semiconductor memory devices incorporate a trim circuit, which can be used to adjust a device's operating voltages following manufacture.
One type of trim circuit comprises a fuse-programmable resistive network in which fuses are selectively programmed to various states to adjust operating voltages such as read and program voltages of a semiconductor memory device. The programming of a trim circuit can be performed in accordance with trim codes, which comprise information corresponding to different adjustment values.
A trim circuit is typically programmed by calibrating trim codes during a test operation. The test operation is typically performed by a test apparatus and can be performed, for instance, at a wafer level or a package level.
In a conventional test operation, the test apparatus reads trim codes from a device under test (DUT). The test apparatus then applies various signals to the DUT according to the trim codes and calibrates the trim codes according to the DUT's responses to the signals. The different trim codes can correspond to different operating modes of the DUT. Accordingly the different trim codes can be calibrated according to the different operating modes. Following the test operation, the calibrated trim codes are programmed into the DUT.